In recent years, along with the development of imaging optical system technology, research and development has been conducted on a display device that displays an image so that the image is visually recognized as if the image was superimposed on an external image (hereinafter also referred to as superimpose an image). Such a display device includes a display device which has, for example, a half mirror or the like which displays an image (virtual image) while allowing external light to pass through the half mirror, and is mounted on the head.
However, in a case where the image is superimposed on the external image, the greater the difference between the convergence angle for the external image and the convergence angle for the image is, the greater the burden on the user observing the image and the external image is.
With respect to this, Patent Literature 1 discloses an invention relating to a glasses-type display device in which depending on the observation position of the user, the optical axis of image light and the optical axis of image light parallel to the image light are moved in a horizontal direction with respect to these optical axes. Hence, the difference between the convergence angle for the image and the convergence angle of the external image is adjusted to decrease, thereby reducing the burden on the user.